In super- or hypermarkets, cabinets of the shelving type are known, which comprise a back from which issue superposed shelves are surmounted by a top and rest on a base, the assembly which constitutes an open enclosure through which a flow of cold air passes to ensure refrigeration and good conditions for conservation of the products.
Display furniture is also known, particularly for products of the "delicatessen" type, which comprises a display surface completed by a window preferably curved rearwardly. This surface has a flow of cold air passing thereover, as hereinabove, to maintain the products at a low temperature compatible with good conditions of conservation.
In presently known systems, a decentralized refrigerating unit is used, for example in service premises, which, in conventional manner by compression (condensation) and expansion (evaporation), is able to take from the outside environment the calories necessary for the latent heat of vaporization of the refrigerating liquid and consequently, the production of cold. The condensation unit is connected by appropriate conduits to each of the containers to which it sends the refrigerating fluid in the liquid state, with the interposition of an electrovalve controlled by a thermostat, the electrovalve being opened or closed as a function of the needs of cold in the assembly which the enclosures served.
The refrigerating fluid passes from the liquid phase to the vapor phase via an evaporator which has a constantly circulating air flow passing therethrough. The air flow passes over the finned tubes of the evaporator towards the back and the top of the cabinet from which it is distributed via orifices and nozzles to sweep all the products located in the open enclosure. The air is recovered at the base of the cabinet and reheated by passage over the stored products which are returned on the evaporator.
As the temperature on the wall of the evaporator is lower than 0.degree. and the circulating air is laden with humidity, this results in the formation and accumulation of frost which must be periodically eliminated with the aid of electric resistors. During the periods of defrosting, with production of calories by the electric resistors, circulation of the refrigerating liquid and ventilation is interrupted. This brings about an undesirable rise in the temperature within the cabinet and of the products that it contains.
According to another method, defrosting is obtained by maintaining ventilation and by stopping the circulation of the refrigerating fluid, for example, for 30 to 45 minutes every 6 hours.
FIG. 1 of the accompanying drawings schematically shows a cabinet 3 which comprises a plurality of shelves 3a, 3b, 3c and which is supplied with refrigerant from a refrigerating unit.
The latter comprises a compressor 1a, a coil 1b for evacuating the heat resulting from the compression and a store 1c of refrigerating fluid in the liquid state (high pressure).
This refrigerating fluid reaches the cabinet 3 via appropriate conduits, after passage via an electrovalve 2 as a function of needs of cold as indicated hereinabove. The refrigerating fluid then passes through the pressure reducing valve 4 controlled by the thermostatic train 5 to arrive at the evaporator 6 where cold is produced by passage of the refrigerating fluid from the liquid phase to the gaseous phase.
Although this technique has certain advantages, it does present several drawbacks:
(1) Each cabinet presents a large number of refrigerating components, which increases their cost and in the event of momentary breakdown, makes necessary interventions on these components difficult. In the case of a breakdown, the cabinets must be emptied and the interventions must be carried out at night or on Sundays, which represents long and expensive handling operations thereby handicapping the conditions for exploitation.
(2) It is not possible to monitor the concealed components directly and visually because they are generally located behind the rear face or in the back of the cabinet.
(3) The system does not allow for filtration of the circulating cold air.
(4) The possibilities of change in the arrangements and architecture of the interior decoration of the stores are reduced and also expensive.
(5) Finally, the periodic defrostings cause undesirable rises in temperature which increase the refrigerating balance of the exploitation and are detrimental to the conservation of the products.